Active stylus

ABSTRACT

An active stylus includes a signal processing section. The signal processing section during operation in a first mode, while supplying a downlink signal DS 1 , obtained by modulating a pulse train signal with a pen pressure level P, to an electrode, determines whether it is necessary to switch to a second mode. The signal processing section during operation in the second mode, while supplying a downlink signal DS 2 , obtained by modulating a sine wave signal with the pen pressure level P, to the electrode, determines whether it is necessary to switch to the first mode. The signal processing section switches to operation in the second mode when determining that such is necessary, and switches to operation in the first mode when determining that such is necessary. The active stylus may be used with two position detection devices, one supporting only the first method and the other supporting only the second method.

TECHNICAL FIELD

The present invention relates to an active stylus and, in particular, toan active stylus that supports a plurality of detection methods.

BACKGROUND ART

An active capacitive position detection system is known, which useselectrodes provided in a touch panel to detect a finger to additionallydetect the presence and position of a stylus. A stylus used for thistype of position detection system is called an “active stylus” and isconfigured such that a signal can be sent therefrom, via capacitivecoupling with the electrodes, to a sensor controller provided in aposition detection device. The sensor controller detects the presenceand position of the stylus by detecting this signal.

As an example of such an active stylus, Patent Document 1 discloses astylus configured to send to the sensor controller both a positionsignal used to derive coordinate data and a data signal representinginformation such as pen pressure value and unique stylus identifier(ID).

Patent Document 2 discloses another example of an active stylus. Thestylus according to this example sends pen pressure detection results ina digital form. Also, in Patent Document 2, a position detection deviceincludes a display device and a transparent sensor. The positiondetection device detects not only a position pointed to by a stylus anda pen pressure but also a position touched by a finger.

Numerous electronic apparatuses have come along that include a stylusconfigured to send signals using capacitive coupling. A plurality ofsignal transmission methods not compatible with each other have comeinto use as position detection systems included in these electronicapparatuses. Specifically, there exists a mixture of a method that usesa signal obtained by modulating a pulse train signal (including a pulsesignal and a rectangular wave signal) as a signal sent by the stylus(hereinafter referred to as a “first method”) and a method that uses asignal obtained by modulating a sine wave signal (hereinafter referredto as a “second method”) as a signal sent by the stylus.

Patent Document 3 discloses an example of a position detection systemthat conforms to the first method. The stylus according to this exampleincludes a pen pressure detector and a signal transmission section. Thepen pressure detector optically detects a pen pressure. As illustratedin FIG. 10 of Patent Document 3, signals sent by the signal transmissionsection include a position signal pulse 910 used by the positiondetection device to detect a stylus position and a pressure signal pulse950 indicating a pen pressure level detected by the pen pressuredetector. The position signal pulse 910 is sent intermittently, and thepressure signal pulse 950 is sent in-between transmissions of theposition signal pulses 910 only during detection of a pen pressure (whennot in a hovering state). The position signal pulse 910 includes analternating current (AC) pulse at a given frequency (specifically,28.125 Hz), and the pressure signal pulse 950 includes afrequency-modulated pulse signal.

Patent Document 4 also discloses an example of a position detectionsystem that conforms to the first method. The stylus according to thisexample includes a TX drive circuit 680 as illustrated in FIG. 9 ofPatent Document 4, and the stylus is configured to send a TX signal 677,which is a pulse train signal similar to a TX signal 632 used duringfinger detection. The TX signal 677 is detected by a controller viacapacitive coupling between the stylus and the sensor.

It should be noted that Patent Document 4 also discloses an arrangementfor boosting during transmission of a signal by the stylus (paragraph0084). According to this, a booster 870 is provided in the stylus topermit amplification of a TX signal 835 by a chip drive circuit 890 thatis responsible for sending the TX signal 835.

In contrast, the position detection systems disclosed in PatentDocuments 1 and 2 conform to the second method. A stylus according tothe second method is configured to modulate a sine wave signal, ratherthan a pulse train signal such as a signal used during finger detection(signal sent from the sensor controller to the transmitting electrodeinside the sensor), in accordance with the pen pressure level and so on,and send the modulated signal. Specifically, for example, the stylusaccording to the second method is configured to modulate a carriersignal at several hundred to several MHz by amplitude shift keying (ASK)or on-off-keying (OOK) and send the modulated signal. In order toextract the signal at the above frequency, the sensor controllerreceives the signal via a band-pass filter and recovers the pen pressurevalue.

PRIOR ART DOCUMENT Patent Documents

-   Patent Document 1: PCT Patent Publication No. WO2015/111159-   Patent Document 2: Japanese Patent Laid-Open No. 2014-63249-   Patent Document 3: U.S. Pat. No. 8,536,471-   Patent Document 4: U.S. Patent Application Publication No.    2012-0105362

SUMMARY OF INVENTION Technical Problem

A position detection device that supports only the second method isunable to receive transmission signals from a stylus that supports onlythe first method, and a position detection device that supports only thefirst method is unable to receive transmission signals from a stylusthat supports only the second method. As a result, for example, when auser attempts to alternately use position detection devices side byside, one supporting only the first method and another supporting onlythe second method, each time the user switches from one positiondetection device to the other, the user must switch the styluses,resulting in inconvenience.

A possible solution to this would be to configure the stylus to send atransmission signal generated by the first method (e.g., signal obtainedby modulating a pulse train signal) and a transmission signal generatedby the second method (e.g., signal obtained by modulating a sine wavesignal) alternately. The method in which the stylus is configured inthis manner will be hereinafter referred to as an “alternatetransmission method.” According to the alternate transmission method, itis possible for both the position detection device supporting only thefirst method and the position detection device supporting only thesecond method to receive transmission signals of the stylus, eliminatingthe need to switch the styluses each time the position detection deviceis switched. However, it is normally unlikely that both of the positiondetection devices are used at once. In this method, therefore, one ofthe signals is always sent uselessly. This is not preferred from theviewpoint of reducing the power consumption of the stylus.

According to one aspect of the invention, even when position detectiondevices are used side by side alternately, one supporting only the firstmethod and another supporting only the second method, an active styluswould lower power consumption than the alternate transmission method andwould eliminate the need to switch styluses each time the positiondetection device is switched from one to the other.

Technical Solution

An active stylus is provided, which sends information in associationwith a change in an electric field to a sensor controller via capacitivecoupling with a sensor. The active stylus includes a core body, anelectrode, a pen pressure detector, a power supply, and a signalprocessing section. The core body forms a pen tip. The electrode isprovided near the core body. The pen pressure detector detects a penpressure level proportional to a pen pressure applied to the core body.The signal processing section operates in one of first and second modesbased on power supplied from the power supply. During operation in thefirst mode, the signal processing section, while supplying a firsttransmission signal, obtained by modulating a pulse train signal withthe pen pressure level, to the electrode, determines whether or not itis necessary to switch to the second mode. During operation in thesecond mode, the signal processing section, while supplying a secondtransmission signal, obtained by modulating a sine wave signal with thepen pressure level, to the electrode, the signal processing sectiondetermines whether or not it is necessary to switch to the first mode.When determining that it is necessary to switch to the second mode, thesignal processing section switches to operation in the second mode, andwhen determining that it is necessary to switch to the first mode, thesignal processing section switches to operation in the first mode.

An active stylus according to another aspect of the present inventionincludes a core body, an electrode, a pen pressure detector, a powersupply, and a signal processing section. The core body forms a pen tip.The electrode is provided near the core body. The pen pressure detectordetects a pen pressure level proportional to a pen pressure applied tothe core body. The signal processing section operates in one of firstand second modes based on power supplied from the power supply. Duringoperation in the first mode, the signal processing section, whilesupplying a first transmission signal, obtained by modulating a pulsetrain with the pen pressure level, to the electrode, determines whetheror not it is necessary to switch to the second mode based on a signalreceived during a time period in which the first transmission signal isnot sent. During operation in the second mode, the signal processingsection, while supplying a second transmission signal, generated by amodulation method different from the modulation method in which thepulse train is modulated with the pen pressure level, to the electrode,determines whether or not it is necessary to switch to the first mode.When determining that it is necessary to switch to the second mode, thesignal processing section switches to operation in the second mode, andwhen determining that it is necessary to switch to the first mode, thesignal processing section switches to operation in the first mode.

Advantageous Effect

According to the present invention, the stylus determines whether or notit is necessary to switch between modes, and the operation mode of thestylus is switched in accordance with the determination result. As aresult, the first mode can be used as the operation mode of the styluswhen the stylus is used together with a position detection device thatsupports only the first method, and the second mode can be used as theoperation mode of the stylus when the stylus is used together with aposition detection device that supports only the second method.Therefore, the stylus can be configured not to send a secondtransmission signal when used together with a position detection devicethat supports only the first method, and not to send a firsttransmission signal when used together with a position detection devicethat supports only the second method. As a result, when positiondetection devices are used side by side, one supporting only the firstmethod and another supporting only the second method, it is possible toensure lower power consumption than the alternate transmission methoddescribed above and eliminate the need to change (switch) styluses eachtime the position detection device is switched from one to the other.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram illustrating a configuration of a position detectionsystem 1 according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating the manner in which the positiondetection system 1 according to the embodiment of the present inventionis used.

FIG. 3 is a diagram illustrating a configuration of a position detectiondevice 3 according to the embodiment of the present invention.

FIG. 4 is a diagram illustrating a configuration of a stylus 2 accordingto a comparative art of the present invention.

FIG. 5 is a diagram illustrating an example of a data signal d1Dgenerated by a control section 90 a illustrated in FIG. 4 (in the caseof an on-off-modulated pulse train signal).

FIG. 6 is a diagram illustrating another example of the data signal d1Dgenerated by the control section 90 a illustrated in FIG. 4 (in the caseof a frequency-modulated pulse train signal).

FIG. 7 is a diagram illustrating an example of a data signal d2Dgenerated by the control section 90 a illustrated in FIG. 4 (in the caseof an on-off modulated sine wave signal).

FIG. 8 is a flowchart illustrating processes performed by the controlsection 90 a illustrated in FIG. 4.

FIG. 9 is a diagram illustrating an example of a signal generated by thecontrol section 90 a illustrated in FIG. 4.

FIG. 10 is a diagram illustrating a configuration of the stylus 2according to a first embodiment of the present invention.

FIG. 11 is a flowchart illustrating processes performed by a controlsection 90 b illustrated in FIG. 10.

FIG. 12 is a flowchart illustrating in detail operation in a first modeillustrated in FIG. 11.

FIG. 13 is a flowchart illustrating in detail operation in a second modeillustrated in FIG. 11.

FIG. 14 is a diagram illustrating an example of a signal generated bythe control section 90 b illustrated in FIG. 10.

FIG. 15 is a diagram illustrating a configuration of the stylus 2according to a second embodiment of the present invention.

FIG. 16 is a flowchart illustrating in detail operation in the secondmode handled by a control section 90 c illustrated in FIG. 15.

FIG. 17 is a diagram illustrating an example of a signal generated bythe control section 90 c illustrated in FIG. 15.

FIG. 18 is a diagram illustrating a configuration of the stylus 2according to a third embodiment of the present invention.

FIG. 19 is a flowchart illustrating in detail operation in the firstmode handled by a control section 90 d illustrated in FIG. 18.

FIG. 20 is a flowchart illustrating in detail operation in the secondmode handled by the control section 90 d illustrated in FIG. 18.

FIG. 21 is a diagram illustrating an example of a signal generated bythe control section 90 d illustrated in FIG. 18.

FIG. 22 is a diagram illustrating a configuration of the stylus 2according to a fourth embodiment of the present invention.

FIG. 23 is a diagram illustrating a configuration of the stylus 2according to a fifth embodiment of the present invention.

DETAILED DESCRIPTION

A detailed description will be given below of embodiments of the presentinvention with reference to accompanying drawings.

FIG. 1 is a diagram illustrating a configuration of a position detectionsystem 1 according to an embodiment of the present invention. Asillustrated in FIG. 1, the position detection system 1 includes a stylus2 and a position detection device 3.

The stylus 2 is a position pointer that has a function to send adownlink signal DS to the position detection device 3 and a function toreceive an uplink signal US sent by the position detection device 3. Thedownlink signal DS sent by the stylus 2 includes two kinds of downlinksignals DS1 and DS2 (first and second transmission signals) in differentformats. As illustrated in FIG. 9 which will be described later, thedownlink signal DS1 is a signal that includes a burst signal d1B, anon-modulated pulse train signal, and a data signal d1D obtained bymodulating a pulse train signal. Among specific examples of the downlinksignal DS1 are a downlink signal based on the modulation methoddescribed in Patent Document 3, and a downlink signal comprising a pulsetrain signal similar to a pulse train signal supplied to a transmittingelectrode of a mutually capacitive touch panel or in a correlatedmanner. On the other hand, the downlink signal DS2 is a signal thatincludes a burst signal d2B, a non-modulated sine wave signal, and adata signal d2D obtained by modulating a sine wave signal. A specificexample of the downlink signal DS2 is a downlink signal used, forexample, in the active electrostatic (ES) (trademark) method.

The stylus 2 is configured to include a core body 20, an electrode 21, apen pressure detector 22, a switch 23, a signal processing section 24,and a power supply 25 as illustrated in FIG. 1.

The core body 20 is a rod-shaped member that is arranged such that itslongitudinal direction agrees with the direction of a pen axis of thestylus 2 and makes up a pen tip of the stylus 2. The surface of a frontend portion of the core body 20 is coated with a conductive material toform the electrode 21. A rear end portion of the core body 20 is incontact with the pen pressure detector 22. The pen pressure detector 22detects a pen pressure level (pen pressure level P illustrated in FIG. 4and so on which will be described later) proportional to the pressureapplied to the front end of the core body 20 (pen pressure applied tothe core body 20) when the pen tip of the stylus 2 is pressed against atouch surface 3 a (described later) of the position detection device 3or the like. In a specific example, the pen pressure detector 22includes a variable capacitance module whose capacitance changes withpen pressure.

The electrode 21 is a conductor provided near the core body 20 and iselectrically connected to the signal processing section 24 by wiring.When the signal processing section 24 supplies the downlink signal DS tothe electrode 21, electric charge proportional to the supplied downlinksignal DS is induced in the electrode 21. As a result, the capacitancein a sensor 30 which will be described later changes, allowing theposition detection device 3 to receive the downlink signal DS bydetecting this change. Also, when the uplink signal US sent by theposition detection device 3 arrives at the electrode 21, electric chargeproportional to the incoming uplink signal US is induced in theelectrode 21. The signal processing section 24 receives the uplinksignal US by detecting the electric charge induced in the electrode 21.

The switch 23 is, for example, a side switch provided on a lateral sideof a housing of the stylus 2 and serves as an input section configuredto accept user operation. Specifically, the switch 23 is configured tooutput switch information SW illustrated in FIG. 4 and so on describedlater in accordance with a state produced by user operation (pressedstate). The switch information SW is information indicating one of twostates, such as ON and OFF.

The signal processing section 24 has a function to receive the uplinksignal US sent by the position detection device 3 via the electrode 21and has a function to generate the downlink signal DS (downlink signalsDS1 and DS2) and send the signal via the electrode 21 to the positiondetection device 3. It should be noted that the uplink signal US mayinclude a command as will be described later. In that case, the signalprocessing section 24 acquires the command by demodulating and decodingthe received uplink signal US and generates the downlink signal DS inaccordance with the acquired command.

The power supply 25 is used to supply operating power (direct current(DC) power) to the signal processing section 24 and includes, forexample, a cylindrical AAAA battery.

The position detection device 3 is configured to include the sensor 30,a sensor controller 31, and a system controller 32 as illustrated inFIG. 1. The sensor 30 forms the touch surface 3 a. The system controller32 controls the respective sections of the position detection device 3including the sensor 30 and the sensor controller 31.

The sensor controller 31 has a function to receive the downlink signalDS sent by the stylus 2 via the sensor 30 and a function to send theuplink signal US via the sensor 30 toward the stylus 2.

Although only one position detection device 3 is illustrated in FIG. 1,the sensor controller 31 can be classified into a type that can receivethe downlink signal DS1 but cannot receive the downlink signal DS2(position detection device 3 supporting only the first method describedabove) and a type that can receive the downlink signal DS2 but cannotreceive the downlink signal DS1 (position detection device 3 supportingonly the second method described above). The stylus 2 according to thepresent embodiment is characterized in that it is configured to offerlower power consumption than the alternate transmission method, whichwill be described with reference to FIGS. 4 to 9, and eliminate the needto change (switch) the styluses 2 each time the position detectiondevice 3 is switched from one to the other when these two positiondetection devices 3 are used side by side.

FIG. 2 is a diagram illustrating an example of the manner in which theposition detection system 1 is used. FIG. 2 illustrates an example inwhich position detection devices 3A and 3B, which are two types of theposition detection devices 3 each illustrated in FIG. 1, are placed sideby side on a desk and a single user inputs a picture into the positiondetection device 3A and text into the position detection device 3B,respectively, by using a single stylus 2. The present invention iseffective in such a case. It should be noted that, in the exampleillustrated in FIG. 2, each of the position detection devices 3A and 3Bis connected to a server not depicted via an access point 5, and thatthe server combines the picture input into the position detection device3A and the text input into the position detection device 3B into asingle document.

FIG. 3 is a diagram illustrating a configuration of the positiondetection device 3. FIG. 3 illustrates the configurations of the abovetwo types of position detection devices 3 as merged together, and thesections involved in sending the uplink signal US is a configurationspecific to the type of the position detection device 3 capable ofreceiving the downlink signal DS2. In other words, the type of theposition detection device 3 not capable of receiving the downlink signalDS2 does not have a function to send the uplink signal US.

As illustrated in FIG. 3, the sensor 30 is configured so that aplurality of linear electrodes 30X and a plurality of linear electrodes30Y are arranged in a matrix fashion, and the sensor 30 is capacitivelycoupled with the stylus 2 by these linear electrodes 30X and 30Y. Thesensor 30 is used not only to detect the stylus 2 but also to detectfingers. Also, the sensor controller 31 is configured to include atransmitting section 60, a selecting section 40, a receiving section 50,a logic section 70, and a memory control unit (MCU) 80.

The transmitting section 60 is a circuit for sending the uplink signalUS illustrated in FIG. 1. Specifically, the transmitting section 60 isconfigured to include a pattern supply section 61, a switch 62, aspreading process section 63, a code sequence holding section 64, and atransmission guard section 65. Although a description will be givenassuming that the pattern supply section 61 is included in thetransmitting section 60 in the present embodiment, the pattern supplysection 61 may be included in the MCU 80.

The pattern supply section 61 retains a detection pattern c1 and has afunction to continuously and repeatedly output a signal (or bit string)that matches with the detection pattern c1 during a given continuoustransmission period (e.g., 3 milliseconds) in accordance with theinstruction of a control signal ctrl_t1 supplied from the logic section70. The pattern supply section 61 also has a function to output a givendelimiting pattern STP at least twice in a row immediately after the endof this continuous transmission period or when the transmission ofcontrol information c2 described later begins.

The detection pattern c1 is a symbol value pattern used by the stylus 2to detect the presence of the sensor controller 31 and is known to thestylus 2 in advance (before the stylus 2 detects the sensor controller31). A symbol refers to a unit of information used for modulation in atransmission process (unit of information represented by a transmissionsignal) and to a unit of information obtained by demodulating onesymbol, which is a reception signal, in a reception process. A symbolvalue can include a value converted into a bit string (hereinafterreferred to as a “value associated with a bit string”) and a value notconverted into a bit string by the stylus 2 that has received the symbol(hereinafter referred to as a “value not associated with a bit string”).As illustrated in Table 1 depicted later, a symbol pertaining to theformer takes on values whose number is a power of two and can beassociated with a bit string such as “0001.” The bit length of eachsymbol denoted by a bit string as described above is determined by thespecification of the spreading process section 63. On the other hand, asymbol pertaining to the latter takes on one or more values (e.g., twovalues) and takes on values that are not associated with bit stringssuch as “P,” “M,” and so on, as illustrated in Table 1 below. In theexample illustrated in Table 1 below, “P” and “M” are associated with agiven spreading code sequence and an inverted code sequence thereof,respectively.

A detection pattern c1 is expressed by a pattern of values notassociated with bit strings. Specifically, the detection pattern c1 ismade up of a repetition of “P” and “M,” such as “PMPMPM . . . .”

The delimiting pattern STP is a symbol pattern for notifying the stylus2 of the end of the continuous transmission period described above andis made up of a symbol pattern that does not appear in the repeateddetection pattern c1. For example, if the detection pattern c1 is madeup of a repetition of “P” and “M,” such as “PMPMPM . . . ” as describedabove, the delimiting pattern STP can be made up of a pattern “PP” whichis two consecutive occurrences of “P”. The configurations of thedelimiting pattern STP and the detection pattern c1 may be reversed sothat the delimiting pattern STP is made up of “PM” and the detectionpattern c1 is made up of “PP.”

The switch 62 has a function to select one of the pattern supply section61 and the MCU 80 based on a control signal ctrl t2 supplied from thelogic section 70 and supply the selected one of the outputs to thespreading process section 63. When the switch 62 selects the patternsupply section 61, the spreading process section 63 is supplied with thedetection pattern c1 or the delimiting pattern STP. On the other hand,when the switch 62 selects the MCU 80, the spreading process section 63is supplied with the control information c2 from the MCU 80.

The control information c2 includes a command indicating details of aninstruction issued to the stylus 2 and is generated by the MCU 80. Thecontrol information c2 differs from the detection pattern c1 in that thecontrol information c2 includes a symbol value (e.g., 0 to 15)associated with a bit string having an arbitrary length (e.g., 4 bitlength) and in that the value is not shared with the stylus 2 inadvance. Also, the control information c2 differs from the detectionpattern c1 that includes the values “P” and “M” in that the controlinformation c2 is represented by “D,” which is a value represented by abit string having an arbitrary length (e.g., 4 bit length), i.e., one ofa power-of-two (e.g., 16) number of values that can be represented by abit string having the arbitrary length.

The code sequence holding section 64 has a function to generate andretain an 11-chip-long spreading code PN having an autocorrelationcharacteristic based on a control signal ctrl t3 supplied from the logicsection 70. The spreading code PN retained by the code sequence holdingsection 64 is supplied to the spreading process section 63.

The spreading process section 63 has a function to obtain a 12-chip-longtransmission chip sequence by modulating the spreading code PN retainedby the code sequence holding section 64 based on the symbol value(information represented by the transmission signal as a result of theprocess performed by the spreading process section 63) supplied via theswitch 62. A description will be given below of this function by citinga specific example.

In the example described below, we assume that the detection pattern c1,the delimiting pattern STP, and the control information c2 are made upof combinations of 0 to 15, which are values associated with bit strings(associated bit strings “0000” to “1111”), and “P” and “M,” which arevalues not associated with bit strings, respectively. We also assumethat the spreading code PN retained by the code sequence holding section64 is “00010010111.” In this case, the spreading process section 63converts each of the symbol values (0 to 15 and P and M) into atransmission chip sequence in accordance with Table 1 depicted below.

TABLE 1 Symbol Associated Bit Shift Transmission Chip Value StringPolarity Amount Sequence P Nonassociated Noninverted 0 100010010111(reference) 0 0000 Noninverted +2 111000100101 1 0001 Noninverted +3111100010010 3 0011 Noninverted +4 101110001001 2 0010 Noninverted +5110111000100 6 0110 Noninverted +6 101011100010 7 0111 Noninverted +7100101110001 5 0101 Noninverted +8 110010111000 4 0100 Noninverted +9(−2) 101001011100 M Nonassociated Inverted 0 011101101000 (reference) 81000 Inverted +2 000111011010 9 1001 Inverted +3 000011101101 11 1011Inverted +4 010001110110 10 1010 Inverted +5 001000111011 14 1110Inverted +6 010100011101 15 1111 Inverted +7 011010001110 13 1101Inverted +8 001101000111 12 1100 Inverted +9 (−2) 010110100011

As illustrated in Table 1, the symbol value “P” is converted into atransmission chip sequence made up of “1” followed by the spreading codePN of “00010010111” in this example. Also, each of the symbol values “0”to “7” is converted into a transmission chip sequence made up of “1”followed by a code sequence obtained by cyclically shifting thespreading code PN of “00010010111” by the shift amount illustrated inTable 1. Other symbol values “M” and “8” to “15” are converted intotransmission chip sequences obtained by inverting the transmission chipsequences associated, respectively, with the symbol values “P” and “0”to “7.”

The spreading process section 63 is configured to obtain thetransmission chip sequences by the conversion process described aboveand supply the sequences to the transmission guard section 65.

The transmission guard section 65 has a function to insert a guardperiod, which is a period during which neither transmission norreception is conducted to facilitate switching between transmission andreception operations, between a transmission period of the uplink signalUS and a reception period for receiving a signal from the stylus 2 basedon a control signal ctrl t4 supplied from the logic section 70.

The selecting section 40 is a switch that switches between thetransmission period, during which signals are sent from the sensor 30,and the reception period, during which signals are received by thesensor 30, based on control performed by the logic section 70.Describing specifically, the selecting section 40 is configured toinclude a switch 44 x, a switch 44 y, a conductor selection circuit 41x, and a conductor selection circuit 41 y. The switch 44 x operates,based on a control signal sTRx supplied from the logic section 70, insuch a manner as to connect the output end of the transmitting section60 to the input end of the conductor selection circuit 41 x during thetransmission period and connect the output end of the conductorselection circuit 41 x to the input end of the receiving section 50during the reception period. The switch 44 y operates, based on acontrol signal sTRy supplied from the logic section 70, in such a manneras to connect the output end of the transmitting section 60 to the inputend of the conductor selection circuit 41 y during the transmissionperiod and connect the output end of the conductor selection circuit 41y to the input end of the receiving section 50 during the receptionperiod. The conductor selection circuit 41 x operates, based on acontrol signal selX supplied from the logic section 70, in such a manneras to select one or a plurality of the plurality of linear electrodes30X and connect the selected one or ones to the switch 44 x. Theconductor selection circuit 41 y operates, based on a control signalselY supplied from the logic section 70, in such a manner as to selectone or a plurality of the plurality of linear electrodes 30Y and connectthe selected one or ones to the switch 44 y. The plurality of linearelectrodes 30X or the plurality of linear electrodes 30Y are selected bythe conductor selection circuit 41 x or 41 y, for example, when theuplink signal US is sent from the entire touch surface 3 a.

The receiving section 50 is a circuit for receiving the downlink signalDS (downlink signal DS1 or downlink signal DS2) sent by the stylus 2based on a control signal ctrl _r of the logic section 70. Specifically,the receiving section 50 is configured to include an amplifying circuit51, a detecting circuit 52, and an analog-digital (AD) converter 53.

The amplifying circuit 51 amplifies the downlink signal DS supplied fromthe selecting section 40 and outputs the amplified signal. The detectingcircuit 52 is a circuit that generates a voltage proportional to thelevel of the output signal of the amplifying circuit 51. The ADconverter 53 is a circuit that generates a digital signal by samplingthe voltage output from the detecting circuit 52 at a given timeinterval. The digital signal output by the AD converter 53 is suppliedto the MCU 80.

The receiving section 50 included in the type of the position detectiondevice 3 that can receive the downlink signal DS1 but cannot receive thedownlink signal DS2 is configured to receive a non-modulated pulse trainsignal or a signal obtained by modulating a pulse train signal but isconfigured not to (configured to be unable to) receive a non-modulatedsine wave signal or a signal obtained by modulating a sine wave signal.In this case, therefore, a digital signal is supplied to the MCU 80 fromthe receiving section 50 only when the downlink signal DS1 arrives atthe sensor 30. On the other hand, the receiving section 50 included inthe type of the position detection device 3 that can receive thedownlink signal DS2 but cannot receive the downlink signal DS1 isconfigured to receive a non-modulated sine wave signal or a signalobtained by modulating a sine wave signal but is configured not to(configured to be unable to) receive a non-modulated pulse train signalor a signal obtained by modulating a pulse train signal. In this case,therefore, a digital signal is supplied to the MCU 80 from the receivingsection 50 only when the downlink signal DS2 arrives at the sensor 30.

The logic section 70 and the MCU 80 are control sections that controltransmission and reception operations of the transmitting section 60 andthe receiving section 50. Describing specifically, the MCU 80 is amicroprocessor that includes a read only memory (ROM) and a randomaccess memory (RAM) therein and operates based on a given program. Onthe other hand, the logic section 70 is configured to output therespective control signals described above based on control performed bythe MCU 80. Also, the MCU 80 is configured to perform a process ofderiving coordinate data x and y and so on indicating the position ofthe stylus 2 based on the digital signal supplied from the AD converter53, and outputting the coordinate data to the system controller 32. TheMCU 80 further performs a process of obtaining data Res represented bythe digital signal supplied from the AD converter 53 and outputting thedata Res to the system controller 32 when the digital signal indicatesthe data signal d1D or the data signal d2D.

A detailed description will be given below of a configuration of thestylus 2 and processes performed by the stylus 2. First, the stylus 2that employs the alternate transmission method described above will bedescribed, and then the stylus 2 in first to fifth embodiments of thepresent invention will be described.

FIG. 4 is a diagram illustrating a configuration of the stylus 2according to a comparative art of the present invention. The stylus 2illustrated in FIG. 4 employs the alternate transmission methoddescribed above and corresponds to the comparative art of the presentinvention. The stylus 2 was invented by the inventor of the presentinvention similar to the stylus 2 in the first to fifth embodimentsdescribed later and was not known to the public as of the priority dateof the present application.

As illustrated in FIG. 4, the stylus 2 employing the alternatetransmission method is configured to include an amplifying section 26 aswell as the signal processing section 24 and the power supply 25illustrated also in FIG. 1. The signal processing section 24 isconfigured to include a control section 90 a, a step-up section 91, anoscillating section 92 a, and a switch section 93 a. It should be notedthat although FIG. 4 does not illustrate a function relating to thereception of the uplink signal US of the functions of the signalprocessing section 24, the stylus 2 employing the alternate transmissionmethod may also have a function relating to the reception of the uplinksignal US as does the stylus 2 according to each of the embodiments ofthe present invention which will be described later.

The step-up section 91 has a function to generate a DC voltage V1 byincreasing the DC voltage supplied from the power supply 25. In aspecific example, the step-up section 91 includes a DC-DC converter or acharge pump circuit.

The oscillating section 92 a has a function to generate a non-modulatedsine wave signal that oscillates at a given frequency (carrier signal)by performing an oscillating action based on the DC voltage suppliedfrom the power supply 25. The amplifying section 26 has a function togenerate a non-modulated sine wave signal v2 by amplifying the sine wavesignal generated by the oscillating section 92 a with a givenamplification factor. It is preferred that the amplifying section 26should include an amplifying circuit made up of a transformer and acapacitor as illustrated in FIG. 4.

The switch section 93 a is a unipolar triple-throw switch element and isconfigured to include a terminal ‘a’ connected to the output end of thestep-up section 91, a terminal ‘b’ connected to the output end of theamplifying section 26, a terminal ‘g’ connected to power wiring to whicha ground potential is supplied, and a common terminal ‘c’ connected tothe electrode 21.

The control section 90 a is an integrated circuit (IC) that supplies acontrol signal Ctrl for controlling the switch section 93 a and isconfigured to operate based on power supplied from the power supply 25.In a specific example, the control section 90 a may be an applicationspecific integrated circuit (ASIC) or an MCU.

When sending the downlink signal DS1, the control section 90 a controlsthe switch section 93 a such that the switch section 93 a functions as afirst switch section provided between the output end of the step-upsection 91 and the electrode 21. That is, the control section 90 aperforms a process of switching the switch section 93 a between a statein which the terminal ‘a’ is connected to the common terminal ‘c’ and astate in which the terminal ‘g’ is connected to the common terminal ‘c.’The state in which the terminal ‘a’ is connected to the common terminal‘c’ corresponds to the ON state of the first switch section, and thestate in which the terminal ‘g’ is connected to the common terminal ‘c’corresponds to the OFF state of the first switch section.

At a time when the burst signal d1B of the downlink signal DS1 is sent,the control section 90 a performs control in such a manner as to switchthe switch section 93 a periodically at a given interval. When theterminal ‘a’ is connected to the common terminal ‘c,’ the DC voltage V1is the output voltage of the switch section 93 a. On the other hand,when the terminal ‘g’ is connected to the common terminal c,′ the groundpotential is the output voltage of the switch section 93 a. Therefore, anon-modulated pulse train signal is output from the switch section 93 a,serving as the burst signal d1B.

At a time when the data signal d1D of the downlink signal DS1 is sent,on the other hand, the control section 90 a performs control in such amanner as to switch the switch section 93 a in accordance with the dataRes such as the pen pressure level P and the switch information SW. Itshould be noted that the data Res may include other information such asidentification information of the stylus 2. The control section 90 agenerates the data signal d1D, a pulse train signal modulated based onthe data Res, through this switching control.

Numerous methods are possible as specific methods used by the controlsection 90 a to modulate a pulse train signal. A description will begiven below of a case in which on-off modulation is used and a case inwhich frequency modulation is used by depicting specific examples.

FIG. 5 is a diagram illustrating an example of the data signal d1Dgenerated by the control section 90 a (in the case of an on-offmodulated pulse train signal). In this case, the control section 90 aswitches the switch section 93 a to the terminal ‘a’ side when thetarget bit of the data Res to be sent is “1” and switches the switchsection 93 a to the terminal ‘g’ side when the target bit of the dataRes to be sent is “0.” As a result, the data signal d1D becomes a binarysignal which assumes a high level (=DC voltage V1) when the target bitto be sent is “1” and assumes a low level (=ground potential) when thetarget bit to be sent is “0” as illustrated in FIG. 5

FIG. 6 is a diagram illustrating another example of the data signal d1Dgenerated by the control section 90 a (in the case of afrequency-modulated pulse train signal). In this case, the controlsection 90 a switches the switch section 93 a at a frequency thatmatches with the value of the data Res. For example, FIG. 6 illustratesan example in which when the data Res is 8-bit data and the valueexpressed by this 8-bit data is x, the control section 90 a performscontrol in such a manner as to switch the switch section 93 a at afrequency N-x×m[Hz]. As illustrated in this example, the data signal d1Din this case is a pulse train signal that oscillates at a frequency thatmatches with the value of the data Res.

Referring back to FIG. 4, when sending the downlink signal DS2, thecontrol section 90 a controls the switch section 93 a such that theswitch section 93 a functions as a second switch section providedbetween the output end of the amplifying section 26 and the electrode21. That is, the control section 90 a performs a process of switchingthe switch section 93 a between a state in which the terminal ‘b’ isconnected to the common terminal ‘c’ and a state in which the terminal‘g’ is connected to the common terminal ‘c.’ The state in which theterminal ‘b’ is connected to the common terminal ‘c’ corresponds to theON state of the second switch section, and the state in which theterminal ‘g’ is connected to the common terminal ‘c’ corresponds to theOFF state of the second switch section.

At a time when the burst signal d2B of the downlink signal DS2 is sent,the control section 90 a keeps the switch section 93 a set to theterminal ‘b’ side. Therefore, the non-modulated sine wave signal v2 isoutput from the switch section 93 a, serving as the burst signal d2B.

At a time when the data signal d2D of the downlink signal DS2 is sent,on the other hand, the control section 90 a performs control in such amanner as to switch the switch section 93 a in accordance with the dataRes such as the pen pressure level P and the switch information SW. Itshould be noted that, also in this case, the data Res may include otherinformation such as identification information of the stylus 2. Thecontrol section 90 a generates the data signal d2D, which is a sine wavesignal modulated based on the data Res, through this switching control.

On-off modulation is used by the control section 90 a as a specificmethod of modulating a sine wave signal.

FIG. 7 is a diagram illustrating an example of the data signal d2Dgenerated by the control section 90 a (in the case of an on-offmodulated sine wave signal). The control section 90 a switches theswitch section 93 a to the terminal ‘b’ side when the target bit of thedata Res to be sent is “1” and switches the switch section 93 a to theterminal ‘g’ side when the target bit of the data Res to be sent is “0.”As a result, the data signal d2D is the sine wave signal v2 when thetarget bit to be sent is “1” and is a signal kept at ground potentialwhen the target bit to be sent is “0” as illustrated in FIG. 7.

Here, as can be understood from FIG. 7, when the target bit to be sentis “0,” the state in which nothing is sent is assumed. In order toprevent continuation of this state in which nothing is sent, the controlsection 90 a may generate the data signal d2D by Manchester-coding thedata Res and controlling the switching of the switch section 93 a basedon the Manchester-coded data Res.

Referring back to FIG. 4, the control section 90 a is configured to sendthe downlink signal DS1 and the downlink signal DS2 alternately. This isdesigned to ensure that both the position detection device 3 supportingonly the downlink signal DS1 and the position detection device 3supporting only the downlink signal DS2 can receive a transmissionsignal of the stylus 2. Because the downlink signals DS1 and DS2 aresent alternately, the inventor of the present application calls thismethod the “alternate transmission method.” A detailed description willbe given below.

FIG. 8 is a flowchart illustrating processes performed by the controlsection 90 a. On the other hand, FIG. 9 is a diagram illustrating anexample of a signal generated by the control section 90 a. It should benoted that the horizontal axis in FIG. 9 indicates time and that theupper side of the horizontal axis indicates transmission Tx and thelower side thereof indicates reception Rx. The description will becontinued below with reference to these figures.

First, as illustrated in FIG. 9, the control section 90 a is configuredto repeat a process of sending the downlink signals DS1 and DS2 at aregular interval T1. During each interval T1, the control section 90 aperforms a process of sending the burst signal d1B of the downlinksignal DS1, the data signal d1D of the downlink signal DS1, the burstsignal d2B of the downlink signal DS2, and the data signal d2D of thedownlink signal DS2 in this order. The transmission of the downlinksignal DS1 is conducted by using a time d1 (d1<T1) during the intervalT1, and the transmission of the downlink signal DS2 is conducted byusing a time d2 (d2=T1−d1) during the interval T1. It should be notedthat generally d1<d2.

Here, it is preferred that specific values of T1 and d2 should beselected such that the transmission interval of the downlink signal DS2sent by the control section 90 a is equal to the transmission intervalof the downlink signal DS2 sent by the stylus that supports only thetransmission of the downlink signal DS2 (i.e., stylus that has nofunction to send the downlink signal DS1). This allows the sensorcontroller 31 to receive the downlink signal DS2 at the same interval aswhen the stylus supporting only the transmission of the downlink signalDS2 conducts transmission. It should be noted that, when the stylus ofthe “alternate transmission method” is used to transmit the downlinksignal DS2 having the same data amount as for the stylus supporting onlythe transmission of the downlink signal DS2, it may encounter shortageof time because of the need to also send the downlink signal DS1. Inthat case, however, the transmission data amount of one or both theburst signal d2B and the data signal d2D may be reduced. For example,assuming that a stylus supporting only the transmission of the downlinksignal DS2 sends N symbols per interval, the control section 90 a maysend only M (M<N) symbols within one interval of the interval T1.

The section hatched with polka dots in FIG. 9 represents a section inwhich the sine wave signal v2 is sent. According to this notation, thedata signal d2D is a signal that is sent intermittently as illustratedin FIG. 9. This is in line with the fact that the signal processingsection 24 does not output the sine wave signal v2 when the target bitto be sent is “0” as described with reference to FIG. 7.

Referring to the flowchart in FIG. 8, upon initiating its process, thecontrol section 90 a starts to send the downlink signal DS1 first (stepS1). Thereafter, the control section 90 a monitors the passage of timewhile, at the same time, sending the downlink signal DS1 (step S2) andwhen a given time d1 elapses starts to send the downlink signal DS2(step S3). Thereafter, the control section 90 a monitors the passage oftime while, at the same time, sending the downlink signal DS2 (step S4)and when a given time d2 elapses returns to step S1 and starts to sendthe downlink signal DS1 again. Thus, the control section 90 a sends thedownlink signals DS1 and DS2 alternately. This makes it possible for theposition detection device 3 supporting only the downlink signal DS1 andthe position detection device 3 supporting only the downlink signal DS2to receive a transmission signal of the stylus 2.

According to control performed by the control section 90 a, on the otherhand, the downlink signals DS1 and DS2 are sent repeatedly at all times.This means that either the downlink signal DS1 or DS2 is sent uselesslyat all times, which is not preferred from the viewpoint of reducing thepower consumption of the stylus 2 as described earlier. Such a problemcan be avoided to lower power consumption while eliminating the need tochange styluses each time the position detection device 3 is switchedfrom one to the other. A detailed description will be given below of thefirst to fifth embodiments of the present invention one by one.

FIG. 10 is a diagram illustrating a configuration of the stylus 2according to the first embodiment of the present invention. The stylus 2illustrated in FIG. 10 differs from the stylus 2 illustrated in FIG. 4in that it has a control section 90 b and a switch section 93 b in placeof the control section 90 a and the switch section 93 a. The stylus 2illustrated in FIG. 10 is the same as the stylus 2 illustrated in FIG. 4in all other respects, and the same components will be denoted by thesame reference symbols, and a description will be given with focus onthe differences.

The switch section 93 b is a unipolar quadruple-throw type with aterminal ‘r’ added to the switch section 93 a. The terminal ‘r’ isconnected to a receiving terminal of the control section 90 b via abuffer. Also, the control section 90 b is configured such that theuplink signal US reception function is added to the control section 90 aand is configured to operate in either the first or second mode.

As for the uplink signal US reception function, the control section 90 bis configured to handle transmission and reception in a time-dividedmanner. That is, the control section 90 b is not configured to be ableto handle transmission and reception at the same time. The basicoperation of the control section 90 b for transmission is as describedabove about the control section 90 a. When handling reception, on theother hand, the control section 90 b switches the switch section 93 b tothe terminal ‘r’ side using the control signal Ctrl. This allowselectric charge that appears on the electrode 21 to be supplied to thereceiving terminal of the control section 90 b. As a result, the controlsection 90 b receives the uplink signal US sent by the positiondetection device 3 based on the electric charge supplied as describedabove.

The first mode is a mode in which the stylus 2 sends the downlink signalDS1. On the other hand, the second mode is a mode in which the stylus 2sends the downlink signal DS2. During operation in the first mode, whilegenerating the downlink signal DS1 and supplying the signal to theelectrode 21 by the above process, the control section 90 b performs aprocess of determining whether or not it is necessary to switch to thesecond mode. During operation in the second mode, while generating thedownlink signal DS2 and supplying the signal to the electrode 21 by theabove process, the control section 90 b performs a process ofdetermining whether or not it is necessary to switch to the first mode.The control section 90 b makes these determinations based on whether theuplink signal US has been received or not received in each mode. Then,when determining, as a determination result, that it is necessary toswitch to the second mode, the control section 90 b switches itsoperation to that in the second mode. Also, when determining that it isnecessary to switch to the first mode, the control section 90 b switchesits operation to that in the first mode. A specific description will begiven below.

FIGS. 11 to 13 are flowcharts illustrating processes performed by thecontrol section 90 b. On the other hand, FIG. 14 is a diagramillustrating an example of a signal generated by the control section 90b. It should be noted that the horizontal axis in FIG. 14 indicates timeand that the upper side of the horizontal axis indicates thetransmission Tx and the lower side thereof indicates the reception Rx.The description will be continued below with reference to these figures.

First, as illustrated in FIG. 14, the control section 90 b is configuredto send the downlink signal DS1 intermittently at the regular intervalT1 (given first interval) illustrated also in FIG. 9. This is operationin the first mode. Speaking more specifically, the control section 90 bis configured to send the downlink signal DS1 over the given time d1that is shorter than the interval T1 from the beginning of each of theintervals T1. Because of the intermittent transmission of the downlinksignal DS1 in this manner, there is always a time period during which notransmission operation is conducted within the interval T1. The controlsection 90 b performs detection operation to detect the uplink signal USsent by the position detection device 3 using the electrode 21 by takingadvantage of this time period. Then, the control section 90 b determineswhether or not it is necessary to switch to the second mode inaccordance with this detection result. Therefore, the control section 90b makes a determination as to whether or not it is necessary to switchto the second mode at the interval T1.

After having switched to the second mode, the control section 90 b isconfigured to send the downlink signal DS2 intermittently at the regularinterval d2 (given second interval). It should be noted that the timelength of the interval d2 may be or may not be equal to the given timed2 illustrated in FIG. 9. This intermittent transmission is realized byensuring that, when the target bit to be sent is “1,” the sine wavesignal v2 is output from the signal processing section 24, and that whenthe target bit to be sent is “0,” the sine wave signal v2 is not outputfrom the signal processing section 24 when the data signal d2D is sentas described above. Therefore, the intermittent transmission of thedownlink signal DS2 is conducted during transmission of the data signald2D rather than the burst signal d2B as illustrated in FIG. 14. Thecontrol section 90 b performs the detection operation to detect theuplink signal US sent by the position detection device 3 using theelectrode 21 by taking advantage of this time period during which thesine wave signal v2 is not output from the signal processing section 24thanks to this intermittent transmission. Then, the control section 90 bdetermines at every interval d2 whether or not it is necessary to switchto the first mode in accordance with the detection result.

Referring to the flowchart illustrated in FIG. 11, the control section90 b is configured to execute a subroutine for performing operation inthe first mode (step S10) and a subroutine for performing operation inthe second mode (step S30) alternately. Although a detailed descriptionwill be given with reference to FIGS. 12 and 13, this process differsfrom the process performed by the control section 90 a illustrated inFIG. 8 in that the switching between step S10 and step S30 takes placebased on the result of the determination process for switching betweenthe modes conducted during each subroutine rather than in accordancewith the passage of time. A detailed description will be given below ofthe process performed in each of steps S10 and S30.

FIG. 12 is a flowchart illustrating in detail operation in the firstmode (step S10 illustrated in FIG. 11). As illustrated in FIG. 12, thecontrol section 90 b operating in the first mode starts to send thedownlink signal DS1 (including the burst signal d1B and the data signald1D) first (step S11). Thereafter, the control section 90 b monitors thepassage of time while, at the same time, sending the downlink signal DS1(step S12) and starts to receive the uplink signal US (step S13) whenthe given time d1 elapses. Then, when a given time dr (dr≤T1−d1) elapses(step S14), the control section 90 b terminates the reception of theuplink signal US (step S15), waits until the given interval T1 elapses(step S16), and determines whether or not to maintain the first mode(step S17).

Here, as described above, only the type of the position detection device3 that can receive the downlink signal DS2 has a capability to send theuplink signal US, and the type of the position detection device 3 thatcannot receive the downlink signal DS2 has no capability to send theuplink signal US. Therefore, the fact that the uplink signal US isreceived means that the position detection device 3 capable of receivingthe downlink signal DS2 exists near the stylus 2. For this reason, ifthe uplink signal US was received during current execution of thesubroutine (specifically, from the beginning of the reception of theuplink signal US in step S13 to the end of the reception of the uplinksignal US in step S15), the control section 90 b determines, in stepS17, that the first mode will not be maintained (i.e., will be switchedto the second mode) so that the stylus 2 can send the downlink signalDS2. Conversely, if the uplink signal US was not received during currentexecution of the subroutine, the control section 90 b determines thatthe position detection device 3 capable of receiving the downlink signalDS2 does not exist near the stylus 2 and determines that the first modewill be maintained (i.e., will not be switched to the second mode).

When determining in step S17 that the first mode will be maintained, thecontrol section 90 b returns to step S11 and continues with the process.That is, the subroutine in step S10 illustrated in FIG. 11 (operation inthe first mode illustrated in FIG. 12) is repeated. On the other hand,when determining in step S17 that the first mode will not be maintained,the control section 90 b exits from the subroutine in step S10 andcontinues with the process. As a result, the subroutine in step S30illustrated in FIG. 11 (operation in the second mode illustrated in FIG.13) starts.

FIG. 13 is a flowchart illustrating in detail operation in the secondmode (step S30 illustrated in FIG. 11). As illustrated in FIG. 13, thecontrol section 90 b operating in the second mode starts to send theburst signal d2B first (step S31). The transmission time of the burstsignal d2B is determined in advance, and next, the control section 90 bdetermines whether or not the transmission of the burst signal d2B iscomplete (step S32) by determining whether or not this predeterminedtransmission time has expired.

Next, the control section 90 b performs a loop process targetedsuccessively for each of the bits to be sent making up the data signald2D (each bit of the data Res, however, each bit of the Manchester-codeddata Res if the data Res is Manchester-coded) (step S33). This loopprocess is repeated until the interval d2 elapses (step S38).

In the loop process in step S33, the control section 90 b determinesfirst whether or not the target bit to be sent is “1” (step S34). Inthis process, when the target bit to be sent is “0,” the control section90 b makes a negative determination. When the data Res to be sent doesnot exist, the determination result in step S34 is negative as when thetarget bit to be sent is “0.”

When a negative result is obtained in step S34, the control section 90 bstarts to receive the uplink signal US (step S35). On the other hand,when an affirmative result is obtained in step S34, the control section90 b if engaged in a reception operation to receive the uplink signal USterminates the reception operation (step S36) and then starts to sendone-bit worth of the sine wave signal v2 (step S37).

After starting to receive the uplink signal US in step S35 or afterstarting to send the sine wave signal v2 in step S37, the controlsection 90 b determines whether or not the interval d2 has elapsed (stepS38). Then, when determining that the interval d2 has yet to elapse, thecontrol section 90 b returns to step S34 and repeats the process on thenext target bit to be sent. On the other hand, when determining that theinterval d2 has elapsed in step S38, the control section 90 b determineswhether to exit from the loop process (to return to the first mode) orto repeat the loop process (to maintain the second mode) (step S39).

It is preferred that the determination criterion in step S39 should bethe same as that in step S17 illustrated in FIG. 12. That is, it ispreferred that if the uplink signal US was received during currentexecution of the subroutine (more specifically, from the beginning ofthe reception of the uplink signal US in step S35 to the end of thereception of the uplink signal US in step S36; there are a plurality ofthese time periods existing in the second mode), the control section 90b should determine that the second mode will be maintained (i.e., willnot be switched to the first mode), and that, conversely, if the uplinksignal US was not received during current execution of the subroutine,the control section 90 b should determine that the second mode will notbe maintained (i.e., will be switched to the first mode).

When determining in step S39 that the second mode will be maintained,the control section 90 b returns to step S31 and continues with theprocess. The subroutine in step S30 illustrated in FIG. 11 (operation inthe second mode illustrated in FIG. 13) is repeated. On the other hand,when determining in step S39 that the second mode will not bemaintained, the control section 90 b exits from the subroutine in stepS30 and continues with the process. As a result, the subroutine in stepS10 illustrated in FIG. 11 (operation in the first mode illustrated inFIG. 12) starts.

As described above, in the configuration and operation of the stylus 2according to the present embodiment, the stylus 2 determines whether ornot it is necessary to switch between the modes, and the operation modeof the stylus 2 is switched in accordance with the result. This makes itpossible to select the first mode as the operation mode of the stylus 2when the stylus 2 is used together with the position detection device 3that supports only the reception of the downlink signal DS1 and selectthe second mode as the operation mode of the stylus 2 when the stylus 2is used together with the position detection device 3 that supports onlythe reception of the downlink signal DS2. Therefore, it is possible toconfigure the stylus 2 not to send the downlink signal DS2 when thestylus 2 is used together with the position detection device 3 thatsupports only the reception of the downlink signal DS1 (positiondetection device supporting the first method described above) andconfigure the stylus 2 not to send the downlink signal DS1 when thestylus 2 is used together with the position detection device 3 thatsupports only the reception of the downlink signal DS2 (positiondetection device supporting the second method described above). Whenthese position detection devices 3 are used side by side, it is possibleto ensure lower power consumption than the stylus 2 that employs thealternate transmission method illustrated in FIG. 4 and eliminate theneed to change styluses each time the position detection device 3 isswitched from one to the other.

Next, FIG. 15 is a diagram illustrating a configuration of the stylus 2according to the second embodiment of the present invention. The stylus2 illustrated in FIG. 15 differs from the stylus 2 illustrated in FIG.10 in that it has a control section 90 c in place of the control section90 b. The stylus 2 illustrated in FIG. 15 is the same as the stylus 2illustrated in FIG. 10 in all other respects, and the same componentswill be denoted by the same reference symbols, and a description will begiven with focus on the differences.

The control section 90 c differs from the control section 90 b inprocesses in the second mode and is the same as the control section 90 bin all other respects. Specifically, the control section 90 c isconfigured to determine whether or not the stylus 2 is being used (e.g.,in contact with the touch surface 3 a) during operation in the secondmode, and perform a reception operation to receive the uplink signal USonly when determining that the stylus is not being used. The controlsection 90 c is configured not to perform the reception operation toreceive the uplink signal US when determining that the stylus is beingused. A specific description will be given below.

FIG. 16 is a flowchart illustrating in detail operation in the secondmode handled by the control section 90 c. On the other hand, FIG. 17 isa diagram illustrating an example of a signal generated by the controlsection 90 c. It should be noted that the horizontal axis in FIG. 17indicates time and that the upper side of the horizontal axis indicatesthe transmission Tx and the lower side thereof indicates the receptionRx. The description will be continued below with reference to thesefigures.

As illustrated in FIG. 16, the control section 90 c performs theprocesses in steps S31 and S32 as does the control section 90 b (referto FIG. 13). Thereafter, the control section 90 c determines whether ornot the stylus 2 is being used (step S40). This determination is made,for example, based on whether or not the pen pressure level P is largerthan 0. That is, it may determine that the stylus 2 is being used whenthe pen pressure level P is larger than 0 because there is a highprobability that the stylus 2 is in contact with the touch surface 3 aand may determine that the stylus 2 is not being used when the penpressure level P is 0 or less because there is a high probability thatthe stylus 2 is out of contact with the touch surface 3 a. Also, thecontrol section 90 c may determine that the stylus 2 is being used whenthe switch information SW is ON. In this case, whether or not the stylus2 is being used can be determined based on the user's intention.

When determining that the stylus 2 is being used in step S40, thecontrol section 90 c starts to send the data signal d2D (step S41). Thistransmission is intermittent as illustrated in FIG. 17 when the targetbit to be sent is “0” as described above because the sine wave signal v2is not output from the signal processing section 24. Although thecontrol section 90 b in FIG. 10 performs the reception operation toreceive the uplink signal US by taking advantage of time periodsin-between these intermittent transmissions, the control section 90 c inFIG. 15 does not perform such a reception operation. This is because itwas determined in step S40 that the stylus 2 is being used, and thus itis likely that the stylus 2 continues to be located near the positiondetection device 3 capable of receiving the downlink signal DS2 and thatthere is no need to switch to the first mode.

When determining that the stylus 2 is not being used in step S40, on theother hand, the control section 90 c starts to receive the uplink signalUS (step S42). The reception operation in this case is continuous asalso illustrated in FIG. 17. The continuous reception operation ispossible because there is no need to send the data signal d2D when thestylus 2 is not being used and thus the data signal d2D is not sent.

Thereafter, the control section 90 c continues with the transmission ofthe data signal d2D or the reception of the uplink signal US until theinterval d2 elapses (step S43) and determines whether or not to maintainthe second mode when determining that the interval d2 has elapsed instep S43 (step S44).

In the determination in step S44, the control section 90 c makes anunconditional determination to the effect that the second mode will bemaintained when the reception operation in step S42 is not performed(i.e., when the control section 90 c determines in step S40 that thestylus 2 is being used). In this case, therefore, step S44 can beomitted. When the reception operation in step S42 is performed, on theother hand, the control section 90 c determines whether or not tomaintain the second mode based on the same determination criterion asfor step S39 illustrated in FIG. 13.

When determining in step S44 that the second mode will be maintained,the control section 90 c returns to step S31 and continues with theprocess. As a result, the subroutine in step S30 illustrated in FIG. 11(operation in the second mode illustrated in FIG. 16) is repeated. Whendetermining in step S44 that the second mode will not be maintained, onthe other hand, the control section 90 c exits from the subroutine instep S30 and continues with the process. As a result, the subroutine instep S10 illustrated in FIG. 11 (operation in the first mode illustratedin FIG. 12) starts.

As described above, the configuration and operation of the stylus 2according to the present embodiment makes it possible to obtain aneffect of continuously receiving the uplink signal US for a longerperiod of time than in the first embodiment in addition to the sameeffect as with the stylus 2 according to the first embodiment. Thismakes it possible to receive the uplink signal US with higher accuracythan in the first embodiment.

Next, FIG. 18 is a diagram illustrating a configuration of the stylus 2according to the third embodiment of the present invention. The stylus 2illustrated in FIG. 18 differs from the stylus 2 illustrated in FIG. 10in that it has a control section 90 d in place of the control section 90b. The stylus 2 illustrated in FIG. 18 is the same as the stylus 2illustrated in FIG. 10 in all other respects, and the same componentswill be denoted by the same reference symbols, and a description will begiven with focus on the differences.

The control section 90 d differs from the control section 90 b in thatit determines whether or not it is necessary to switch to the first orsecond mode based on user operation accepted by the switch 23illustrated in FIG. 1 rather than based on whether or not the uplinksignal US has been received. The control section 90 d is the same as thecontrol section 90 b in all other respects. A specific description willbe given below.

FIGS. 19 and 20 are flowcharts illustrating processes performed by thecontrol section 90 d. On the other hand, FIG. 21 is a diagramillustrating an example of a signal generated by the control section 90d. It should be noted that the horizontal axis in FIG. 21 indicates timeand that the upper side of the horizontal axis indicates thetransmission Tx and the lower side thereof indicates the reception Rx.The description will be continued below with reference to these figures.

FIG. 19 is a flowchart illustrating in detail operation in the firstmode (step S10 illustrated in FIG. 11). As illustrated in FIG. 19, thecontrol section 90 d operating in the first mode performs the process instep S11 first as does the control section 90 b (refer to FIG. 12).Thereafter, the control section 90 d waits until the given interval T1elapses without performing the processes in steps S12 to S15 illustratedin FIG. 12 (step S16). Because the processes in steps S12 to S15 are notperformed, the control section 90 d does not receive the uplink signalUS during operation in the first mode as illustrated also in FIG. 21.When the interval T1 elapses, the control section 90 d determines, basedon the switch information SW, whether or not the user issued aninstruction to switch between the modes (step S18). In other words, thecontrol section 90 d determines whether or not it is necessary to switchto the second mode.

When determining in step S18 that the user issued no instruction toswitch between the modes, the control section 90 d returns to step S11and continues with the process. As a result, the subroutine in step S10illustrated in FIG. 11 (operation in the first mode illustrated in FIG.19) is repeated. When determining in step S18 that the user issued aninstruction to switch between the modes, on the other hand, the controlsection 90 d exits from the subroutine in step S10 and continues withthe process. As a result, the subroutine in step S30 illustrated in FIG.11 (operation in the second mode illustrated in FIG. 20) starts.

FIG. 20 is a flowchart illustrating in detail operation in the secondmode (step S30 illustrated in FIG. 11). As illustrated in FIG. 20, thecontrol section 90 d operating in the second mode performs the processesin steps S31 to S38 first as does the control section 90 b (refer toFIG. 13). Therefore, the transmission and reception of each signal inthe second mode is conducted in the same manner as in the firstembodiment, as illustrated in FIG. 21. Thereafter, the control section90 d performs a process of determining, based on the switch informationSW, whether or not the user issued an instruction to switch between themodes (step S50) rather than the determination process in step S 39illustrated in FIG. 13. In other words, the control section 90 ddetermines whether or not it is necessary to switch to the first mode.

When determining, in step S50, that the user issued no instruction toswitch between the modes, the control section 90 d returns to step S31and continues with the process. As a result, the subroutine in step S30illustrated in FIG. 11 (operation in the second mode illustrated in FIG.20) is repeated. When determining in step S50 that the user issued aninstruction to switch between the modes, on the other hand, the controlsection 90 d exits from the subroutine in step S30 and continues withthe process. As a result, the subroutine in step S10 illustrated in FIG.11 (operation in the first mode illustrated in FIG. 19) starts.

As described above, the configuration and operation of the stylus 2according to the present embodiment allows for switching between thefirst mode and the second mode based on user's explicit instruction.Therefore, when the position detection device 3 supporting only thereception of the downlink signal DS1 and the position detection device 3supporting only the reception of the downlink signal DS2 are used sideby side as in the first and second embodiments, it is possible to ensurelower power consumption than the stylus 2 that employs the alternatetransmission method illustrated in FIG. 4 and eliminate the need tochange (switch) styluses each time the position detection device 3 isswitched from one to the other.

It should be noted that although, in the present embodiment, theprocesses of the control section 90 d were configured by modifying stepS39 of the processes of the control section 90 b illustrated in FIG. 13,it is possible to configure the processes of the control section 90 d bymodifying step S44 of the processes of the control section 90 cillustrated in FIG. 16 in the same manner. In this case, it is alsopossible to obtain an effect of permitting the reception of the uplinksignal US with higher accuracy than in the first embodiment as in thesecond embodiment.

Next, FIG. 22 is a diagram illustrating a configuration of the stylus 2according to the fourth embodiment of the present invention. The stylus2 illustrated in FIG. 22 differs from the stylus 2 illustrated in FIG.10 in that it has a control section 90 e and an oscillating section 92 bin place of the control section 90 b and the oscillating section 92 a.The stylus 2 illustrated in FIG. 22 is the same as the stylus 2illustrated in FIG. 10 in all other respects, and the same componentswill be denoted by the same reference symbols, and a description will begiven with focus on the differences.

When generating the data signal d2D making up the downlink signal DS2,while keeping the switch section 93 b switched to the terminal ‘b,’ thecontrol section 90 e controls the oscillating state of the oscillatingsection 92 b (rather than controlling the switching of the switchsection 93 a) in accordance with the data Res such as the pen pressurelevel P and the switch information SW. Specifically, the control section90 e puts the oscillating section 92 b into an oscillating state whenthe target bit to be sent is “1” and puts the oscillating section 92 binto a non-oscillating state when the target bit to be sent is “0.”Also, when generating the burst signal d2B, the control section 90 ekeeps the switch section 93 b switched to the terminal ‘b’ and keeps theoscillating section 92 b in an oscillating state.

As described above, the configuration and operation of the stylus 2according to the present embodiment also makes it possible to send thedownlink signal DS2 from the stylus 2 as with the stylus 2 according tothe first embodiment. The stylus 2 according to the present embodimentis the same as the stylus 2 according to the first embodiment in allother respects. Therefore, when the position detection device 3supporting only the reception of the downlink signal DS1 and theposition detection device 3 supporting only the reception of thedownlink signal DS2 are used side by side as in the first embodiment,the configuration and operation of the stylus 2 according to the presentembodiment also makes it possible to ensure lower power consumption thanthe stylus 2 that employs the alternate transmission method illustratedin FIG. 4 and eliminate the need to change styluses each time theposition detection device 3 is switched from one to the other.

It should be noted that the downlink signal DS2 may be generated notonly by the stylus 2 according to the first embodiment but also by thestyluses 2 according to the second and third embodiments.

Next, FIG. 23 is a diagram illustrating a configuration of the stylus 2according to the fifth embodiment of the present invention. The stylus 2illustrated in FIG. 23 differs from the stylus 2 illustrated in FIG. 10in that it has a rectifying section 94 in place of the step-up section91. The stylus 2 illustrated in FIG. 23 is the same as the stylus 2illustrated in FIG. 10 in all other respects, and the same componentswill be denoted by the same reference symbols, and a description will begiven with focus on the differences.

The rectifying section 94 is a circuit that generates the DC voltage V1by rectifying the sine wave signal v2 output from the amplifying section26 using diodes and a capacitor. The DC voltage V1 generated by therectifying section 94 is supplied to the terminal ‘a’ of the switchsection 93 b.

As described above, the configuration and operation of the stylus 2according to the present embodiment also makes it possible to send thedownlink signal DS1 from the stylus 2 as with the stylus 2 according tothe first embodiment. The stylus 2 according to the present embodimentis the same as the stylus 2 according to the first embodiment in allother respects. Therefore, when the position detection device 3supporting only the reception of the downlink signal DS1 and theposition detection device 3 supporting only the reception of thedownlink signal DS2 are used side by side as in the first embodiment,the configuration and operation of the stylus 2 according to the presentembodiment also makes it possible to ensure lower power consumption thanthe stylus 2 that employs the alternate transmission method illustratedin FIG. 4 and eliminate the need to change styluses each time theposition detection device 3 is switched from one to the other.

Also, the configuration of the stylus 2 according to the presentembodiment eliminates the need for the step-up section 91 and,therefore, can simplify the configuration of the signal processingsection 24.

It should be noted that the same DC voltage V1 as in the presentembodiment may be generated not only by the stylus 2 according to thefirst embodiment but also by the styluses 2 according to the second tofourth embodiments. It should be noted, however, that if the generationof the DC voltage V1 is applied to the stylus 2 according to the fourthembodiment, it is necessary to put the oscillating section 92 b into anoscillating state when the downlink signal DS1 is sent.

Although preferred embodiments of the present invention have beendescribed above, the present invention is not limited by theseembodiments, and the present invention can be carried out in variousforms without departing from the disclosure of the present invention.

For example, when the stylus 2 determines whether to switch between themodes based on whether or not the uplink signal US was received in theabove embodiments, the details of the uplink signal US were notconsidered. However, the stylus 2 may determine whether or not to switchbetween the modes based on the details of the uplink signal US. In thiscase, it becomes possible to switch between the modes of the stylus 2 byan explicit instruction from the sensor controller 31.

Also, in each of the above embodiments, although the uplink signal USwas a signal that included the detection pattern c1, the delimitingpattern STP, and the control information c2, the present invention issuitably applicable to a case in which the uplink signal US is a simpletrigger signal.

DESCRIPTION OF REFERENCE SYMBOLS

-   1 Position detection system-   2 Stylus-   3, 3A, 3B Position detection device-   3 a Touch surface-   6 Access point-   20 core body-   21 Electrode-   22 Pen pressure detector-   23 Switch-   24 Signal processing section-   25 Power supply-   26 Amplifying section-   30 Sensor-   30X, 30Y Linear electrode-   31 Sensor controller-   32 System controller-   40 Selecting section-   41 x, 41 y Conductor selection circuit-   44 x, 44 y Switch-   50 Receiving section-   51 Amplifying circuit-   52 Detecting circuit-   53 Analog-digital converter-   60 Transmitting section-   61 Pattern supply section-   62 Switch-   63 Spreading process section-   64 Code sequence holding section-   65 Transmission guard section-   70 Logic section-   90 a to 90 e Control section-   91 Step-up section-   92 a, 92 b Oscillating section-   93 a, 93 b Switch section-   94 Rectifying section-   Ctrl Control signal-   d1B Burst signal-   d1D Data signal-   d2B Burst signal-   d2D Data signal-   DS1, DS2 Downlink signal-   P Pen pressure level-   Res Data-   STP Delimiting pattern-   SW Switch information-   US Uplink signal-   V1 DC voltage-   v2 Sine wave signal

The invention claimed is:
 1. An active stylus that sends information inassociation with a change in an electric field to a sensor controllervia capacitive coupling formed with a sensor, the active styluscomprising: a core body forming a pen tip; an electrode provided nearthe core body; a pen pressure detector configured to detect a penpressure level proportional to a pen pressure applied to the core body;a power supply; and a signal processing circuit, which includes (i) acontrol circuit and (ii) a switch circuit that controls signal flowbetween the signal processing circuit and the electrode in response to acontrol signal Ctr received from the control circuit, wherein the signalprocessing circuit is configured to operate in one of first and secondmodes based on power supplied from the power supply, during operation inthe first mode, while supplying a first transmission signal, obtained bymodulating a pulse train signal with the pen pressure level, to theelectrode based on operation of the control circuit and the switchcircuit, determine whether or not it is necessary to switch to thesecond mode, during operation in the second mode, while supplying asecond transmission signal, obtained by modulating a sine wave signalwith the pen pressure level, to the electrode based on operation of thecontrol circuit and the switch circuit, determine whether or not it isnecessary to switch to the first mode, and switch to operation in thesecond mode when determining that it is necessary to switch to thesecond mode, and switch to operation in the first mode when determiningthat it is necessary to switch to the first mode.
 2. The active stylusof claim 1, wherein during operation in the first mode, while sendingthe first transmission signal intermittently, the signal processingcircuit performs detection operation to detect an uplink signal sent bya position detection device using the electrode during a time period inwhich the first transmission signal is not sent, and determines whetheror not it is necessary to switch to the second mode in accordance with adetection result of the uplink signal.
 3. The active stylus of claim 2,wherein during operation in the first mode, the signal processingcircuit is configured to send the first transmission signalintermittently at first intervals and determine, at the first intervals,whether or not it is necessary to switch to the second mode.
 4. Theactive stylus of claim 1, wherein during operation in the second mode,while sending the second transmission signal intermittently, the signalprocessing circuit performs detection operation to detect an uplinksignal sent by a position detection device using the electrode during atime period in which the second transmission signal is not sent, anddetermines whether or not it is necessary to switch to the first mode inaccordance with a detection result of the uplink signal.
 5. The activestylus of claim 4, wherein during operation in the second mode, whiledetermining, at second intervals, whether or not it is necessary toswitch to the first mode, the signal processing circuit is configured tosend the second transmission signal intermittently a plurality of timeswithin one of the second intervals.
 6. The active stylus of claim 4,wherein during operation in the second mode, the signal processingcircuit determines whether or not the active stylus is being used andperforms the detection operation to detect the uplink signal whendetermining that the stylus is not being used.
 7. The active stylus ofclaim 6, wherein during operation in the second mode, the signalprocessing circuit determines, based on the pen pressure level, whetheror not the active stylus is being used.
 8. The active stylus of claim 1,further comprising: an input circuit configured to accept useroperation, wherein the signal processing circuit determines, based onthe user operation accepted by the input circuit, whether or not it isnecessary to switch to the first mode or the second mode.
 9. The activestylus of claim 1, wherein the signal processing circuit furtherincludes: a step up circuit configured to increase a voltage suppliedfrom the power supply, wherein the switch circuit includes a firstswitch circuit provided between an output end of the step up circuit andthe electrode, and wherein the control circuit is configured to generatethe first transmission signal by switching the first switch circuit ONand OFF in accordance with the pen pressure level.
 10. The active stylusof claim 9, wherein the control circuit switches the first switchcircuit ON and OFF by on-off modulation or frequency modulation inaccordance with the pen pressure level.
 11. The active stylus of claim9, wherein the signal processing circuit further includes: anoscillating circuit configured to generate a sine wave signal, and anamplifying circuit configured to amplify the sine wave signal, whereinthe switch circuit further includes a second switch circuit providedbetween an output end of the amplifying circuit and the electrode, andwherein the control circuit generates the second transmission signal byswitching the second switch circuit ON and OFF in accordance with thepen pressure level.
 12. The active stylus of claim 11, wherein thecontrol circuit switches the switch section circuit ON and OFF by on-offmodulation in accordance with the pen pressure level.
 13. The activestylus of claim 9, wherein the signal processing circuit furtherincludes: an oscillating circuit configured to generate a sine wavesignal, and an amplifying circuit configured to amplify the sine wavesignal and output the amplified signal to the electrode, wherein thecontrol circuit generates the second transmission signal by controllingthe oscillating circuit in accordance with the pen pressure level. 14.The active stylus of claim 1, wherein the signal processing circuitfurther includes: an oscillating circuit configured to generate a sinewave signal, an amplifying circuit configured to amplify the sine wavesignal, and a rectifying circuit configured to rectify an output signalof the amplifying circuit, wherein the switch circuit includes: a firstswitch circuit provided between an output end of the rectifying circuitand the electrode, and a second switch circuit provided between anoutput end of the amplifying circuit and the electrode, and wherein thecontrol circuit is configured to generate the first transmission signalby switching the first switch circuit ON and OFF in accordance with thepen pressure level while the second switch circuit is set to OFF, and togenerate the second transmission signal by switching the second switchcircuit ON and OFF in accordance with the pen pressure level while thefirst switch circuit is set to OFF.
 15. An active stylus that sendsinformation in association with a change in an electric field to asensor controller via capacitive coupling formed with a sensor, theactive stylus comprising: a core body forming a pen tip; an electrodeprovided near the core body; a pen pressure detector configured todetect a pen pressure level proportional to a pen pressure applied tothe core body; a power supply; and a signal processing circuit, whichincludes (i) a control circuit and (ii) a switch circuit that controlssignal flow between the signal processing circuit and the electrode inresponse to a control signal Ctr received from the control circuit,wherein the signal processing circuit is configured to operate in one offirst and second modes based on power supplied from the power supply,during operation in the first mode, while supplying a first transmissionsignal, obtained by modulating a pulse train with the pen pressure levelusing a first modulation method, to the electrode based on operation ofthe control circuit and the switch circuit, determine whether or not itis necessary to switch to the second mode based on a signal receivedduring a time period in which the first transmission signal is not sent,during operation in the second mode, while supplying a secondtransmission signal, generated by a second modulation method differentfrom the first modulation method in which the pulse train is modulatedwith the pen pressure level, to the electrode based on operation of thecontrol circuit and the switch circuit, determine whether or not it isnecessary to switch to the first mode, and switch to operation in thesecond mode when determining that it is necessary to switch to thesecond mode, and switch to operation in the first mode when determiningthat it is necessary to switch to the first mode.
 16. The active stylusof claim 15, wherein during operation in the second mode, while sendingthe second transmission signal intermittently, the signal processingcircuit performs a detection operation to detect an uplink signal sentby a position detection device using the electrode during a time periodin which the second transmission signal is not sent, and determineswhether or not it is necessary to switch to the first mode in accordancewith a detection result of the uplink signal.
 17. The active stylus ofclaim 16, wherein during operation in the second mode, the signalprocessing circuit determines whether or not the active stylus is beingused and performs the detection operation to detect the uplink signalwhen determining that the stylus is not being used.
 18. The activestylus of claim 17, wherein during operation in the second mode, thesignal processing circuit determines, based on the pen pressure level,whether or not the active stylus is being used.
 19. The active stylus ofclaim 15, further comprising: an input circuit configured to accept useroperation, wherein the signal processing circuit determines, based onthe user operation accepted by the input circuit, whether or not it isnecessary to switch to the first mode or the second mode.